1. Field of the Invention
The present invention relates to a method for manufacturing an internal connector part for a pacer, and to a female connector for pacer.
2. Description of the Prior Art
Implantable pacers normally have a pacer housing (also called can) containing electronic circuitry and a unit for electric power as well as different electrodes which are connected to the interior parts in the pacer housing and which are to be implanted in or in the vicinity of the heart. The electrodes are connected to the pacer by means of leads. The internal parts of the pacers have to be well protected against the internal environment, especially the body fluids in the body for a long period of time, which places strict requirements on all entries into the interior of the can and especially on the connections of the leads to the housing. At the same time it should be possible to disconnect the pacer from the implanted leads for replacement or servicing of the pacer. The connective parts of the pacer and the leads have largely been standardized so as to encompass a relatively deep female socket having a number of contact surfaces whereas the leads are provided with a male part having one or several corresponding peripheral, generally circular contact surfaces.
At present the connective part of the pacer housing containing the female socket is made of a transparent material, normally of epoxy resin, which is molded onto the housing and onto contacts extending outwardly from the housing. The male part of the leads is normally locked by means of set-screws, although other fastening means are known. The positioning and alignment of the different contact surfaces and the fastening means or metallic threads for the set screws prior to the molding of the connective part is, however, very complicated and the delay in the manufacturing process incurred by the curing of the epoxy resin is considerable.
It would thus be desirable if the molding procedure could be dispensed with.
It has been discussed that these complexities could be avoided by designing the pacer with a socket located inside the metal housing but this kind of socket, sometimes termed a “black hole”, is not used at present.
U.S. Pat. Nos. 4,934,366 and 5,324,311, the teachings both of which are incorporated herein by reference, describe two interior sockets or black holes for pacers. Both designs have a tubular member formed by a number of alternating sections made of metal and insulating ceramic, respectively. An end section of metal can be welded or bonded to an opening in the pacer housing by means of a flange. The use of different materials however, requires high standards which regard to precision and durability of the component parts and as well as on the assembly procedure thereof. This is especially important since the interior sockets must meet very high standards regarding the integrity of the interior of the pacer housing during long times of implantation in a demanding environment. The manufacture of these prior art sockets thus is relatively complicated. The same is valid for the device disclosed in U.S. Pat. No. 4,262,982, which discloses a ceramic socket combined with a metal flange for welding to a pacer housing and with a metallic interior contact pin. This device also has locking means in the form of an inwardly directed, circumferential rib located adjacent the opening of socket. This rib is intended to cooperate with barb-shaped sealing rings on the contact plug on the proximal end of the lead or catheter.
Other connectors of the “black hole” type are disclosed in co-pending International Patent Applications No PCT/SE99/01383 (corresponding to co-pending U.S. application Ser. No. 09/763,397) and PCT/SE99/01893 (corresponding to co-pending U.S. application Ser. No. 09/830,259 filed Aug. 20, 2001). These connectors have a metallic tube containing a sintered ceramic plug with a longitudinal bore and a number of metallic contact surfaces in the form of metal rings and/or plugs molded into the ceramic materials.